Torque limiting handle assembly

ABSTRACT

One member of a two member torque limiting handle assembly has resiliently depending legs extending about its rotational axis. The second member has features arranged such that on rotation of said first member, the features contact the legs so that when a reaction torque of the second member is less than a threshold value, the second member rotates with the first member and when a reaction torque of the second member is greater than the threshold value, the legs resiliently deflect so that the features simply pass across said legs and the second member does not rotate with the first member.

BACKGROUND

This invention relates to a torque limiting handle assembly.

A chair control may have a handle which may be rotated by a user to control an adjustment mechanism of the chair. For example, a rotational handle may be employed to control the tension on a spring, which spring resists tilting of the seat or backrest. With any such mechanism there is a risk that the handle may be over-torqued which could damage or jam the mechanism. To avoid this result, it is known to use a two-piece handle assembly connected by a spring loaded ratchet. More specifically, as shown in FIGS. 1 and 2, one piece of the handle assembly acts as the handle 12 and the second piece as a connector 14 connecting to the remainder of the mechanism. The connector 14 has a face gear 16 that meshes with a face gear 18 of the ratchet 20. A spring 22 backstopped by a plate 24 affixed to the connector (by screws 26) urges the ratchet face gear 118 against the connector face gear 16. The handle 12 is keyed to the ratchet 20 so that rotating the handle rotates the ratchet face gear 18. With this arrangement, if the torque on the handle 12 exceeds a threshold (in either rotational direction), the ratchet 20 simply ratchets to allow the handle to turn while the connector 14 remains stationary. Thus, over-torquing of the handle assembly is avoided.

A drawback with such a handle assembly is that it is of relatively complicated construction.

This invention seeks to provide an improved torque limiting handle assembly.

SUMMARY

One member of a two member torque limiting handle assembly has resiliently depending legs extending about its rotational axis. The second member has features arranged such that on rotation of said first member, the features contact the legs so that when a reaction torque of the second member is less than a threshold value, the second member rotates with the first member and when a reaction torque of the second member is greater than the threshold value, the legs resiliently deflect so that the features simply pass across said legs and the second member does not rotate with the first member.

According to the present invention there is provided a torque limiting handle assembly, comprising: a first member having a handle for turning by a user; a second member having a connection end for connection to a member to be torqued; one member of said first member and said second member having a plurality of legs resiliently depending from a body, said legs extending about a rotational axis of said body; another member of said first member and said second member having a coupling section extending along said rotational axis of said body, said coupling section having features arranged such that on rotation of said first member, said features contact said legs so that when a reaction torque of said second member is less than a threshold value, said second member rotates with said first member and when a reaction torque of said second member is greater than said threshold value, said legs resiliently deflect so that said features pass across said legs and said second member does not rotate with said first member.

According to another aspect of the present invention, there is provided a torque limiting handle assembly, comprising: an annular handle member for turning by a user; a shaft member having a rotational axis, said shaft member having a connection end for connection to a member to be torqued and an opposite legged end with a plurality of resiliently depending legs, said legs extending about said rotational axis, said legged end of said shaft member disposed within said handle member such that said legs are within said handle member; said annular handle member having an inside wall with features arranged such that on rotation of said handle member, said features contact said legs so that when a reaction torque of said shaft member is less than a threshold value, said shaft member rotates with said handle member and when a reaction torque of said shaft member is greater than said threshold value, said legs resiliently deflect so that said features pass across said legs and said shaft member does not rotate with said handle member.

Other features and advantages will become apparent from the following description in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the figures which illustrate example embodiments of the invention,

FIG. 1 is a perspective view of a known handle assembly,

FIG. 2 is an exploded view of the handle assembly of FIG. 1,

FIG. 3 is a perspective view of a chair control incorporating a handle assembly made in accordance with this invention,

FIG. 4 is an exploded perspective view of the handle assembly of FIG. 3,

FIG. 5 is an end view of the assembled handle assembly absent the cap,

FIG. 6 is a cross-sectional view of a handle member of the handle assembly, and

FIG. 7 is a exploded cross-sectional fragmentary view of a portion of the handle assembly of FIG. 3

DETAILED DESCRIPTION

Turning to FIG. 3, a chair control 100 has a main frame 112 with one end of a seat plate 114 pivotably joined to the main frame. A spring is disposed between a spring backstop carried by the main frame and the seat plate in order to resist tilting of the seat plate. The position of the spring backstop may be adjusted by an adjustment mechanism in order to change the compression of the spring, and therefore the tension applied by the spring. The adjustment mechanism is operated by torque limiting handle assembly 130.

Referencing FIGS. 4 to 6, the handle assembly 130 has an annular handle member 132 and a shaft member 134 with a rotational axis R. The shaft member has a connection end 138 for connection to the remainder of the spring tension adjustment mechanism. A plurality of legs 140 resiliently depend from the opposite end 142 of the shaft member and extend about the rotational axis R of the shaft member 134. When assembled, the legged end 142 of the shaft member 134 is disposed within the handle member 132 such that the legs 140 face a coupling section 146 of inside wall 144 of the annular handle member.

Coupling section 146 is a portion of inside wall 144 that is featured. More specifically, the coupling section has undulations 148. The outside surface of each leg 140 also has undulations 150. The shaft member 134 and handle member 132 are sized such that undulations 150 of each leg 140 extend within undulations 148 of wall section 146. In consequence, on rotation of the handle member 132, the undulations 148 of the coupling section 146 contact the legs 140 so that when a reaction torque of the shaft member 134 is less than a threshold value, the shaft member rotates with the handle member. On the other hand, when a reaction torque of the shaft member is greater than this threshold value, the legs resiliently deflect so that the undulations 148 of the coupling section 146 pass across the legs and the shaft member does not rotate with the handle member.

Coupling section 146 extends from an open end 152 of the handle member 132 to a shoulder 153 of inside wall 144. The shaft member 134 has a shoulder 154 toward the base of legs 140.

To assemble handle assembly, the connection end 138 of the shaft member is inserted into the open end 152 of the handle member and passed through the opposite open end 156 of the handle member until the shoulder 154 of the shaft member seats against the shoulder 152 of the inside wall 144 of the handle member. In this position, the legs 140 of the shaft member face coupling section 146 of the handle member.

Turning to FIG. 7, a number of tabs 158 project axially from the open end 152 of the handle member. A cap 162 has a like number of tab-receiving openings 164. The cap may be press fit over the tabs 158. By holding the cap to the handle member, the shaft member may be retained within the handle member.

The undulations 150 of each leg 140 extend from the outer end of the leg and terminate part way along the leg spaced from the shoulder 154.

The handle member is a unitary single piece of material. The shaft member is also a unitary single piece of material. And the cap member is also a unitary single piece of material. Each of these members may be fabricated of any suitable material (such as polypropelene or another plastic material, glass filled nylon, or even steel), to provide the resilience which allows the legs to resiliently deflect. The threshold torque applied by the handle member beyond which the legs will deflect may be controlled by the selection of the width and length of the legs and the thickness of the material.

Advantageously, the described torque limiting handle member has only three parts which may be assembled without fasteners. Consequently, the handle assembly may be manufactured at relatively low cost.

In another embodiment, the featured surface of the legs of the legged end of the shaft member is the inner surface of each leg rather than the outer surface. In this instance, the coupling section of the handle member is a cylindrical stub with an outer featured surface. With this embodiment, the coupling section of the handle member is inserted within the legs of the shaft section. To hold the handle member to the shaft member in this embodiment, the handle member could have a plurality of arms resiliently depending therefrom, each provided with a head which snap fits into an annular groove provided in the shaft member.

In a further embodiment, the shaft member 134 has the coupling section and the handle member has the legged end. More specifically, the end of the shaft member 134 opposite connection end 138 is annular with an inside wall being featured to provide the coupling section. In this embodiment, the handle member terminates in a short stub from which a plurality of legs resiliently depend. This handle stub may then be inserted into the annulus at the end of the shaft member so that the featured outer surface of the legs face the features of the coupling section of the shaft member. To hold the handle member to the shaft member in this embodiment, the annular end of the shaft member could have a plurality of arms resiliently depending therefrom, each provided with a head which snap fits into an annular groove provided at the base of the stub of the handle member.

Other modifications will be apparent to those skilled in the art and, therefore, the invention is defined in the claims. 

1. A torque limiting handle assembly, comprising: a first member having a handle for turning by a user; a second member having a connection end for connection to a member to be torqued; one member of said first member and said second member having a plurality of legs resiliently depending from a body, said legs extending about a rotational axis of said body; another member of said first member and said second member having a coupling section extending along said rotational axis of said body, said coupling section having features arranged such that on rotation of said first member, said features contact said legs so that when a reaction torque of said second member is less than a threshold value, said second member rotates with said first member and when a reaction torque of said second member is greater than said threshold value, said legs resiliently deflect so that said features pass across said legs and said second member does not rotate with said first member.
 2. The handle assembly of claim 1 wherein said coupling section has a wall bearing said features.
 3. The handle assembly of claim 2 wherein said wall is undulated, said features comprising undulations in said wall.
 4. The handle assembly of claim 3 wherein a surface of each leg opposed to said wall is undulated and undulations of each leg extend within undulations of said wall.
 5. The handle assembly of claim 4 wherein said coupling section extends around said legs and wherein said wall is an inside wall of said coupling section.
 6. The handle assembly of claim 4 wherein said another member further comprises a seat against which said one member seats to locate said legs within said coupling section.
 7. The handle assembly of claim 6 wherein said first member is said another member and said second member is said one member.
 8. The handle assembly of claim 7 wherein said first member is annular having open ends, said second member partially disposed within said annular first member and projecting through one open end of said first member such that said connection end of said second member projects beyond said one open end of said first member.
 9. The handle assembly of claim 8 wherein said second member is restrained from withdrawal from said first member through said one open end of said first member by said seat and through another open end of said first member by a cap capping said another open end.
 10. The handle assembly of claim 9 wherein said first member comprises a unitary single piece and wherein said second member comprises a unitary single piece.
 11. The handle assembly of claim 10 wherein said cap comprises a unitary single piece.
 12. A torque limiting handle assembly, comprising: an annular handle member for turning by a user; a shaft member having a rotational axis, said shaft member having a connection end for connection to a member to be torqued and an opposite legged end with a plurality of resiliently depending legs, said legs extending about said rotational axis, said legged end of said shaft member disposed within said handle member such that said legs are within said handle member; said annular handle member having an inside wall with features arranged such that on rotation of said handle member, said features contact said legs so that when a reaction torque of said shaft member is less than a threshold value, said shaft member rotates with said handle member and when a reaction torque of said shaft member is greater than said threshold value, said legs resiliently deflect so that said features pass across said legs and said shaft member does not rotate with said handle member.
 13. The handle assembly of claim 12 wherein said inside wall is undulated, said features comprising undulations in said wall.
 14. The handle assembly of claim 13 wherein a surface of each leg opposed to said wall is undulated and undulations of each leg extend within undulations of said wall.
 15. The handle assembly of claim 14 wherein said handle member has a handle member seat and said shaft member has a shaft member seat which seats against said handle member seat in order to locate said legs within said handle member.
 16. The handle assembly of claim 15 wherein said shaft member is restrained from withdrawal from said handle member by a cap attached to said handle member and capping said legged end of said shaft member.
 17. The handle assembly of claim 16 wherein said handle member comprises a unitary single piece and wherein said shaft member comprises a unitary single piece.
 18. The handle assembly of claim 17 wherein said cap comprises a unitary single piece.
 19. The handle assembly of claim 12 wherein said handle member comprises a unitary single piece and wherein said shaft member comprises a unitary single piece. 